Superb spinel law twinned Galena flattened crystals - the twinning occurs on the octahedral face in which it is parallel to....why the crystals are flat, I do not know. Spinel, the mineral in which the twinning is common, does not flatten like this. Anyhow there are at least five good sized crystals to 2cm across. At the bass of the specimen are fantastic and lustrous black Sphalerite crystals. Very nice specimen.